1. Field of the Invention
The present invention relates to control of a passenger protection system for protecting passengers in a car crash and, more particularly, a start controlling method for a passenger protection system and a start controlling system for a passenger protection system. Both are able to distinguish between a low speed crash and a soft crash, and a recording medium for recording a start controlling program for a passenger protection system.
2. Description of the Related Art
In the prior art, it has been well known that, according to the running speed and the crashed part of the vehicle, type of crash of the vehicle is classified into a low speed frontal crash wherein an entire frontal area of the vehicle collides with an object at low speed, a high speed frontal (head-on) crash wherein the entire frontal area of the vehicle collides with the object at high speed, a high speed offset crash wherein a part of the entire frontal area of the vehicle collides with the object at high speed, and others.
In a passenger protection system represented by an air bag system, for example, which can protect a body of the passenger in such crash, normally it is designed that such start control should be executed by taking account of difference in the acceleration of the vehicle in a crash from that in normal running. Various start controlling methods and systems for embodying the same, etc. have been proposed up to now.
A following concept has been proposed as one of start control concepts for the passenger protection system which has been proposed until now. In other words, at first the integral value (speed integral value) of the deceleration (so-called impact acceleration) upon crash is calculated. Then, it is decided whether or not change in the integral value within a predetermined range is continued over a predetermined period of time, i.e., it is decided whether or not stagnation of the integral value is caused. If it has been decided that the stagnation of the integral value is caused, a predetermined value is then added to the integral value. Therefore, the integrated value is advanced rather than the actual integral value, and then start of the air bag is carried out when it is decided that the integrated value has exceeded a predetermined threshold value.
In the meanwhile, while taking account of the stagnation of the speed integral value which is caused in the crash which is generally called as a soft crash such as an oblique crash, an offset crash, a pole crash, etc., the above start controlling method has been proposed to start the airbag without fail, while distinguishing between the soft crash and the high speed crash in which no stagnation of the speed integral value is caused, etc. However, such start controlling method has not been satisfactory in the following respects and therefore has not been employed in practical use.
More particularly, there has been the low speed crash as the case where start of the air bag is not needed. In such low speed crash, change in the speed integral value of the impact acceleration has the stagnation of the speed integral value, like the above-mentioned soft crash. In addition, sometimes a stagnation time of the speed integral value in the low speed crash is close to or resembles that in the soft crash. Therefore, in some cases there has been a possibility that distinctions between the soft crash and the low speed crash become difficult to determine according to the above concep.
The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a start controlling method for a passenger protection system which is suited for practical use and a system for embodying the same, and a recording medium for recording a start controlling program for a passenger protection system.
It is another object of the present invention to provide a start controlling method for a passenger protection system which is able to distinguish between a soft crash and a low speed crash to thus achieve higher practicality and a system for embodying the same, and a recording medium for recording a start controlling program for a passenger protection system.
In order to achieve the above objects of the present invention, according to a first aspect of the present invention, there is provided a start controlling method for a passenger protection system, of controlling start of the passenger protection system which is constructed such that a protection system for protecting passengers in a vehicle is started in response to a start signal supplied from an external device, comprising the steps of:
executing integral of deceleration of a vehicle with respect to time;
calculating a segment length of change in an integral value in a predetermined range of the integral value, which is derived by the integral of time, relative to an elapsed time; and
deciding type of crash by comparing a calculated value of the segment length with a reference value.
Such start controlling method is made based on a following viewpoint. That is, based on the result of study performrd by inventors of the present invention, the stagnation of the integral value is caused in a certain interval of change in the speed integral value as integration of the deceleration with respect to time according to type of crash. The segment length of the integral value relative to the elapsed time becomes different according to the type of crash even in the case where such stagnation of the integral value is caused, so that the types of crashes can be distinguished from each other based on the difference in the segment length.
It is preferable that, when the segment length is to be calculated, the predetermined range of the integral value should be defined by a point of start of the stagnation of the integral value, i.e., the integral value at a start point, and a point of termination of the stagnation of the integral value, i.e., the integral value at an end point. In practice, it is preferable that, since the values are different according to type of the vehicle, etc., such values should be set based on experimental data, or set by taking account of various conditions, etc. as well as experimental data.
More particularly, the present invention is suitable for distinction between the so-called soft crash such as an oblique crash, a pole crash, etc., which needs start of the passenger protection system, and the low speed crash, which does not need start of the passenger protection system.
Therefore, it is preferable that the above reference value should be set to the segment length of change in the integral value in a predetermined range of the integral value, which is derived by the integral of time of the deceleration of the vehicle in a low speed crash, relative to the elapsed time. The type of crash should be decided as the soft crash if the segment length which is larger than the reference value has been calculated.
In order to achieve the above objects of the present invention, according to a second aspect of the present invention, there is provided a start controlling system for a passenger protection system, for controlling start of the passenger protection system which is constructed such that a protection system for protecting passengers in a vehicle is started in response to a start signal supplied from an external device, comprising:
a deceleration deciding means for deciding whether or not deceleration which is input from an external means exceeds a predetermined magnitude;
an integrating means for executing integral of time of the deceleration which is input from the external means to calculate a speed integral value if it has been decided by the deceleration deciding means that the deceleration exceeds the predetermined magnitude;
a segment length calculating means for calculating a segment length in a predetermined range of the speed integral value which is calculated by the integrating means, relative to an elapsed time;
a segment length deciding means for deciding whether or not the segment length which has been calculated by the segment length calculating means exceeds a predetermined value;
an incrementing means for adding a predetermined increment value to the speed integral value at that point of time if it has been decided by the segment length deciding means that the segment length which has been calculated by the segment length calculating means exceeds the predetermined value; and
a decision starting means for generating a start signal for the passenger protection system if it has been decided that a value derived by the incrementing means exceeds a predetermined threshold value.
Such configuration is implemented by the start controlling method set forth in claim 1 so as to enable the start of the passenger protection system. The deceleration deciding means, the integrating means, the segment length calculating means, the segment length deciding means, the incrementing means, and the decision starting means can be implemented by causing the so-called CPU, which has a function of a computer, to execute the predetermined program.
It is preferable that, when the segment length is to be calculated, the predetermined range of the integral value should be defined by a point of start of the stagnation of the integral value, i.e., the integral value at a start point, and a point of termination of the stagnation of the integral value, i.e., the integral value at an end point. In practice, it is preferable that, since the values are different according to type of the vehicle, etc., such values should be set based on experimental data, or set by taking account of various conditions, etc., as well as experimental data.
In addition, the decision starting means may be composed of a threshold value deciding means for deciding whether or not a value derived by the incrementing means exceeds a predetermined threshold value, and a start signal generating means for generating a start signal for the passenger protection system if it has been decided by the threshold value deciding means that the value derived by the incrementing means exceeds the predetermined threshold value.
In order to achieve the above objects of the present invention, according to a third aspect of the present invention, there is provided a start controlling system for a passenger protection system, for controlling start of the passenger protection system which is constructed such that a protection system for protecting passengers in a vehicle is started in response to a start signal supplied from an external device, comprising:
a central processing unit for reading a predetermined program from another external device and then executing predetermined processes by executing the predetermined program;
a memory device for storing a program which is to be executed by the central processing unit in such a manner that the program can be read by the central processing unit;
a digital/analogue converter for converting a digital start signal, which is supplied from the central processing unit to an air bag system, into an analogue signal; and
an interface circuit for converting an output signal of the digital/analogue converter into a predetermined signal which is suited for the air bag system;
wherein the central processing unit
executes integral of time of deceleration of the vehicle, which is input from an external means,
calculates a segment length of change in an integral value in a predetermined range of the integral value, which is derived by the integral of time, relative to an elapsed time,
compares a calculated value of the segment length with a reference value which is the segment length of change in the integral value in a predetermined range of the integral value, which is derived by the integral of time of the deceleration of the vehicle in a low speed crash, relative to the elapsed time,
decides that type of crash is a soft crash if it has been decided that the calculated value of the segment length is larger than the reference value,
decides whether or not a speed integral value exceeds a predetermined threshold value if it has been decided that the type of crash is the soft crash, and outputs a start signal of an air bag system if it has been decided that the speed integral value exceeds the predetermined threshold value.
In order to achieve the above objects of the present invention, according to a fourth aspect of the present invention, there is provided a recording medium for recording a plurality of computer-readable instructions, comprising:
a first instruction means for causing a computer to decide whether or not deceleration which is input from an external means exceeds a predetermined magnitude;
a second instruction means for causing the computer to execute integral of time of the deceleration to calculate a speed integral value if it has been decided that the deceleration which is input from the external means exceeds the predetermined magnitude;
a third instruction means for causing the computer to calculate a segment length in a predetermined range of the speed integral value being calculated, relative to an elapsed time;
a fourth instruction means for causing the computer to decide whether or not the segment length being calculated exceeds a predetermined value;
a fifth instruction means for causing the computer to add a predetermined increment value to the speed integral value at that point of time if it has been decided that the segment length being calculated exceeds the predetermined value;
a sixth instruction means for causing the computer to decide whether or not the speed integral value, to which the predetermined increment value is added, exceeds a predetermined threshold value; and
a seventh instruction means for causing the computer to generate a start signal to start a passenger protection system if it has been decided that the speed integral value exceeds the predetermined threshold value.